Fig. 3 shows the relative density e

Fig. 3 shows the relative density evolution of ZnO ceramics as a function of CSP and HS dwell time. In both cases, very high relative densities (>98%) can be already achieved with a dwell time of 0 min.The difference in relative density between the two processes is less than 2%. For both the cold sintering and hydrothermal sintering, the evolution of the relative density with time is nonlinear as a decrease followed by an increase in the density after dwell times of 20 and 40 min is observed for cold sintering and hydrothermal sintering, respectively.